Try searching eBay using "record album shipping boxes"
Never used these, so no idea. There are a few posters that do ship albums, but I forget who or would page them. Hopefully they will respond.
They key in my mind is rigidity and toughness. Not so much that the box will bend, but that it could sustain another HEAVY box falling on it. Think whatever box the album is in resting at an angle with only support on two edges and then a heavy box falling on it. That to me spells at least double-walled box if not triple walled.
